Claudin-1 (CLDN1)

Class

CLDN1-targeted antibody-drug conjugate (tubulin inhibitor payload)

Pathway

Antibody binds a CLDN1 epitope exposed on tumor cells (normally hidden in tight junctions), internalizes, releases tubulin inhibitor payload

Claudin-1 is a protein that forms tight junctions, the seals between neighboring epithelial cells that control what passes between them. In healthy tissue, most of CLDN1's surface is folded inward at these junctions, largely hidden from circulating antibodies. In many tumors, normal tissue architecture breaks down and CLDN1 becomes exposed on the outer cell surface, creating a recognition site that is far less accessible on well-organized normal epithelium. This selective exposure is exploited by antibody-drug conjugates, which pair an antibody that binds the exposed CLDN1 epitope with a cytotoxic payload, in this case a tubulin inhibitor that blocks the microtubule assembly cells need to divide. After the antibody binds the tumor cell surface, the complex is internalized and processed, releasing the payload inside the cell, where it disrupts the mitotic spindle and triggers cell death. This strategy is explored across solid tumors where CLDN1 becomes aberrantly displayed, aiming to concentrate cytotoxic drug delivery in malignant tissue while limiting exposure of normal organs. It reflects a broader antibody-drug conjugate rationale: using tumor-restricted surface markers as delivery vehicles for potent chemotherapeutic payloads too toxic to administer systemically on their own.